1. Field of the Invention
The present invention relates to a transmission apparatus, a subrack, and a connector unit, and more particularly to a transmission apparatus, a subrack, and a connector unit each having a shield structure for enhancing EMC (Electro Magnetic Compatibility) performance thereof.
2. Description of the Related Art
Recent transmission apparatuses can be equipped with ATM (Asynchronous Transfer Mode)/LAN (Local Area Network) functions in addition to the existing SONET (Synchronous Optical Network)/SDH (Synchronous Digital Hierarchy) systems. In this case, a plurality of transmission lines are cross-connected via the transmission apparatus.
FIG. 34 shows the appearance of a conventional transmission apparatus. The conventional transmission apparatus 900 has a shield rack 910 housing a subrack 920. The shield rack 910 has a door 911 attached to the front face thereof for opening and closing the shield rack 910. Further, the shield rack 910 has an upper wall thereof formed with openings 912, 913 for receiving cables therethrough.
The subrack 920 also has a door 922 attached to the front face thereof for opening and closing the subrack 920. The subrack 920 houses a plurality of electronic circuit units 921 to which are connected various cables inserted through the openings 912, 913 from the outside of the shield rack 910. The cables connected to the plurality of electronic circuit units 921 include metallic cables 931, 932 and optical fiber cables 933, 934.
In the transmission apparatus 900 constructed as above, the shield rack 910 shields the plurality of internal electronic circuit units 921 and the various cables received therein from external electromagnetic waves, for improvement of EMC performance of the electronic circuit units 921 and the cables.
In recent years, with improvement of processing capabilities, the number of cables to be connected to electronic circuit units in a transmission apparatus tend to be increased. Therefore, the conventional transmission apparatus 900 is required to have the openings 912, 913 increased in open area so as to receive an increased number of cables.
However, if the openings 912, 913 are increased in open area, it can cause degradation of the EMC. In addition, recently, electronic circuit units tends to have higher operating frequencies, and hence there are more exacting demands for EMC performance of such units.
It is an object of the invention to provide a transmission apparatus, a subrack, and a connector unit which are capable of maintaining excellent EMC performance even if an increased number of cables are connected thereto.
To attain the above object, according to a first aspect of the invention, there is provided a transmission apparatus including a plurality of communication interfaces. The transmission apparatus comprises a subrack including a back wiring board, a first connector arranged on a front surface of the back wiring board, and a second connector arranged on a rear surface of the back wiring board and electrically connected to the first connector, an electronic circuit unit connected to the first connector on the back wiring board, and a connector unit including a connector board on which are mounted a male seat connector connected to the second connector on the back wiring board and an external line connector electrically connected to the male seat connector, and a metal case for covering the connector board.
To attain the above object, according to a second aspect of the invention, there is provided a subrack that is capable of housing a plurality of communication interfaces. The subrack comprises a back wiring board, an electronic circuit unit-receiving block arranged on a front surface of the back wiring board, for receiving an electronic circuit unit, a first connector provided in the electronic circuit unit-receiving block, for connection with the electronic circuit unit, a connector unit-receiving block arranged on a rear surface of the back wiring board, for receiving a connector unit including a connector board on which are mounted a male seat connector and an external line connector electrically connected to the male seat connector, and a metal case for covering the connector board, and a second connector provided in the connector unit-receiving block, for electrical connection with the first connector and connectable with the male seat connector of the connector board.
To attain the above object, according to a third aspect of the invention, there is provided a connector unit for electrically connecting between an electronic circuit unit having a communication interface function and an external cable. The connector unit comprises a connector board on which are mounted a male seat connector connectable to a connector provided in a subrack which is capable of housing the electronic circuit board, and an external line connector electrically connected to the male seat connector, and a metal case for covering the connector board.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.